Garry's Mod Black Screen

Okay, so, about a month ago, I load up Garry’s Mod. I start up a map in sandbox. It takes a moment because my computer is kind of crap. When the map finally loads, I can’t see anything. The screen is completely black. But here is the weird part. When I try to walk around, I hear footsteps, and when I press ESC and open my menu, I can here the beeps as I move my cursor along the menu buttons.
I have tried everything from restarting Garry’s Mod, to uninstalling the entire game and reinstating it(BTW: I didn’t go in and delete all the files, so that might still be an issue).

Here are some of my specs, if they will help:
Windows 8.1
Intel® Celeron® CPU 877 @1.40GHz
RAM: 4.00 GB (3.89 GB usable)

And here is a console log after I try to load a map:
Both ConVars must be marked FCVAR_REPLICATED for linkage to work (r_VehicleViewDampen)
Initializing Awesomium…
Both ConVars must be marked FCVAR_REPLICATED for linkage to work (r_VehicleViewDampen)
No Kinect SDK
Lua JIT is DISABLED!
Unknown command “cl_thirdperson”
Unknown command “hud_showemptyweaponslots”
Unknown command “sv_backspeed”
Not playing a local game.
PREP OK
Lua JIT is DISABLED!
Using map cycle file ‘mapcycle.txt’. (‘cfg/mapcycle.txt’ was not found.)
Nav File is wrong or something (1)
Garry’s Mod

sandbox
gm_flatgrass
1
76561198066073322
Attemped to precache unknown particle system “generic_smoke”!
Warning: WorldTwoTextureBlend found on a non-displacement surface (material: gm_construct/flatgrass). This wastes perf for no benefit.
clientside lua startup!
Lua JIT is DISABLED!
Requesting texture value from var “$dummyvar” which is not a texture value (material: NULL material)
Compact freed 847872 bytes
Redownloading all lightmaps
Dropped cinichecuk from server (Disconnect by user.)

Thanks.

Do you have this problem in any other Source games (HL2, CSS, TF2)? Make sure your graphics drivers are up to date, and try reducing the graphics settings in the options

I don’t have this problem with any game at all, just Garry’s Mod. My graphics drivers are all up to date and my graphic settings are all at the minimum.

Does anyone know how to fix this?

I assume it’s possibly one of post processing effects or an addon. Remove any addons and try removing the “postprocess” folder located in “Steam\steamapps\common\GarrysMod\garrysmod\lua”.

Well, I did both of those things, and now everything is okay! Thanks so much!